This application relates to placing economizer injection ports through the wrap of one of the scroll members in a scroll compressor and providing an indentation to enhance injection and improve unloading operation.
Scroll compressors are becoming widely utilized in refrigerant compression applications. As known, a pair of scroll members each has a base with a generally spiral wrap extending from the base. Typically, one scroll is non-orbiting and the other scroll orbits relative to the non-orbiting scroll. The orbiting scroll contacts the non-orbiting scroll to seal and define compression chambers. The compression chambers are moved toward a central discharge port as the orbiting scroll orbits relative to non-orbiting scroll. Originally scroll compressors tended to have relatively thin wraps. More recently, so called “hybrid” wraps have been developed wherein the thickness of the wrap varies along its length.
Refrigerant systems are also making increasing use of an economizer cycle in which an additional heat exchange process occurs and a portion of the refrigerant is directed back to the intermediate compression point within the compressor. At this intermediate point in the compression cycle, this refrigerant is injected into the compressor compression chambers through an economizer line and then into the compressor internal injection ports. This has the effect of increasing both system capacity and efficiency. The scroll compressor designer seeks to optimize the size and location of the internal injection ports to maximize the efficiency and capacity benefits as mentioned above.
The economizer ports were originally formed through the base of the non-orbiting scroll penetrating into the compression chambers. Typically, the injection occurred through the economizer injection ports at a point in the compression cycle when the refrigerant is sealed off from suction to define a first compression chamber. After the seal off point, the injection ports continue to communicate with the compression chambers for a significant period of the cycle, while at the same time the pressure within the compression chamber while initially relatively low continues to increase. This increase in pressure inside compression chambers results in refrigerant being pumped back into the economizer line. This produces so called pumping losses, and hence decreased compressor efficiency which is undesirable.
An improved scroll compressor is disclosed in U.S. Pat. No. 6,430,959. In this compressor, economizer fluid is injected into the compression chambers through ports formed within the wrap of the non-orbiting scroll. The wrap is of a “hybrid” profile such that it has varying thicknesses along its length.
The orbiting scroll member has small grooves formed in the floor of its base plate. When the ports are aligned with these grooves, economizer flow is injected into the compression chamber. However, once the orbiting scroll has moved such that the port is no longer aligned with the groove, the facing base plate of the orbiting scroll closes the port off. In this way, the scroll compressor designer is able to easily control the “on/off” time for the economizer injection into the compression chamber.
However, with this configuration a situation may arise that either the size of a port is not large enough or the port is not open for a sufficient time to inject a sufficient amount of vapor into the compression pocket. In particular this situation, would occur more often with regard to a port located at a thicker portion of the wrap.
Thus, while the above-described scroll compressor has proven quite successful, it would be desirable to further enhance the injection of the fluid through at least one of the two injection ports.